README.md: Update build instructions using new config names

Author: bramoosterhuis

README.md

@@ -22,20 +22,22 @@ To get started with Lithosphere, follow these steps:
     make \
         -C buildroot \
         BR2_EXTERNAL="${PWD}/buildroot-external-metrological-restricted:${PWD}/buildroot-external-metrological-open-source" \
-        O=${PWD}/raspberrypi3_wpe \
-        raspberrypi3_wpe_defconfig
+        O=${PWD}/raspberrypi_aarch64_wpe \
+        raspberrypi_aarch64_wpe_defconfig
     ```
 
 1. Build the image:
     ``` shell
-    cd raspberrypi3_wpe
+    cd raspberrypi_aarch64_wpe
     make
     ```
     or
     ``` shell
-    make -C raspberrypi3_wpe
+    make -C raspberrypi_aarch64_wpe
     ```
 
+> Note: There are additional defconfigs available for different hardware platforms or configurations. You can explore them in the `configs` directory of the repository and choose the one that best suits your needs.
+
 ## Updating the layers :arrows_clockwise:
 
 To update the Lithosphere project, follow these steps: